Sunlight can break up clusters of titanium dioxide nanoparticles to increase their transport into the skin, according to scientists from the University of California, US.

Their study showed that sunlight reduced the size of nanoparticles. In tests on pigskin, the light-exposed nanoparticles showed far more penetration than those tested in the dark. “These results suggest that photoinduced disaggregation may have important health implications,” say the researchers.